Could the damage be coming from the Mortar Volley itself?
Get KB-> Hit a wall ->Get hit by the Mortar AoE while trying to run under the shield.
15:04:12.094 Stormcaller Blast Tank's Defensive Systems hits Kemenotic for 843 kinetic damage, causing 843 threat.
That is on 8 man, i doubt it would be hitting for over 2k on 16 man, so it is still very little amount of damage as long as you're topped off and fly back into a shield and not in the middle of no where.
You can find the complete log here.